In recent years, a PTT (Push To Talk) system has been widely used. In the PTT system, a telephone conversation is not conducted on a one-to-one basis as seen in a general telephone conversation. Instead, a plurality of communication terminals constitute a group, and audio is transmitted from one of the communication terminals within the group to all the rest of the communication terminals within the group. The PTT system uses a transceiver communication system, whereby a speaker can transmit audio only while a PTT button of a communication terminal is being pressed. A listener receives audio from any speaker within the group. Accordingly, the listener needs to identify the current speaker based on, for example, his/her voice or the name of the speaker shown on a display of a communication terminal of the listener.